Redirecting Excited‐State Proton Transfer Through Supramolecular Polymerization in Nanoconfinement

The photoluminescence of photoacids in supramolecular assemblies provides crucial insights into proton transfer (PT) processes within biologically relevant confinement. In this work, we present a strategy to activate intermolecular excited‐state PT within the hydrophobic cavities of cyclodextrin‐based nanotubes. Activation is achieved using a specifically designed amphoteric emitter which undergoes a pKa inversion in the photoexcited state. Despite this photophysical behavior, intramolecular PT does not occur due to the spatial separation between the proton donor and acceptor sites in the compound. However, in the presence of γ‐cyclodextrin, the photoacid assembles into guest pairs, enabling pre‐organized PT between neighboring molecules. The effects of confinement on photostability, emission lifetime, and quantum yield indicate a mechanistic shift from excited‐state protolytic dissociation to intermolecular excited‐state PT. Spectroscopic investigation of the assembly mechanism and solvent isotope effect further supports the role of a template effect, reminiscent of enzymatic activation, in facilitating PT in the excited state.